The invention relates to a semiconductor device comprising a semiconductor body whose surface is provided, at least at the location of a PN junction, with a silicon oxide layer, methyl-substituted silyloxy groups being formed on the surface of the silicon oxide layer.
Such a method is described in French Patent 1.273.319. In this patent use is made of trimethyl methoxy silane. Using small quantities of water this compound hydrolyzes to trimethyl silanol and methanol. Subsequently, trimethyl silanol reacts with hydroxyl groups on the surface of the silicon oxide layer to form trimethyl silyloxy groups.
However, the methanol present may also convert the hydroxyl groups on the surface of the silicon oxide layer into methoxy groups. As a consequence hereof the surface of the silicon oxide layer is not optimally occupied by methylated silyloxy groups, thus enabling moisture from the environment to migrate to the semiconductor body via the silicon oxide layer and thereby increasing the leakage current over the PN junction.